Public Function CarExists reg As String As Boolean Using constring As New OleDb. String object that contains zero characters. Newbies generally face difficulty in understanding these three methods. Click Here to Expand Forum to Full Width Advertiser Disclosure: Some of the products that appear on this site are from companies from which QuinStreet receives compensation. ToString End If I see what you're going for there.
For more information about streaming, see. Additional columns or rows are ignored. Have you decided if you want to use ExecuteScalar or an output parameter to that one can help for the solution you choosed. Join your peers on the Internet's largest technical computer professional community. I understand why I am getting the error - the db query is returning null - as it should.
IsNullOrEmpty method IsNullOrEmpty is a convenience method that enables you to simultaneously test whether a String is Nothing or its value is Empty. Why not just use the result of the comparison in the first place? ToInt32 objValue ; } In case someone else runs across this post, one note to add to your fix. ExecuteScalar Catch ex As Exception Console. Empty strings are used quite commonly in various programming scenarios to represent a blank text field. Hi, Got a bit of a bizarre issue here, I am trying to use ExecuteScalar to see if any values are present and depending if it is to perform a certain action.
Examples The following example creates a and then executes it using. Could you please quote the full error message? Why are you getting the exception? An empty string is an instance of a System. I can check the object as to whether or not it is null. ExecuteScalar If lJobName Is Nothing Then 'Do something with the error condition Else 'Do something with lJobName which contains a valid result. Still, String holds a value of Nothing just fine. I'm really stumped on this one, the errors happening in both cases.
End If Of course this doesn't help you if you cause a SqlException, but it should handle the problem of no rows found in the result set. String objects are immutable, meaning that they cannot be changed once they have been created. Is that the wrong way of looking at it? ExecuteNonQuery, ExecuteScalar and ExecuteReader are for different purposes. ToInt32 objValue ; } In case someone else runs across this post, one note to add to your fix. How to check null String in vb. Now you can go where they get things done! This code was giving me errors i just fiddled with it until i got it to half work.
Close ; } Public Sub CreateOracleCommand myScalarQuery As String, connection As OracleConnection Dim command As New OracleCommand myScalarQuery, connection command. This is necessary since if you set AllowPaging to True and bind GridView using DataReader then you will land into an Exception as DataReader fetches records in ForwardOnly Mode. Problem is it will always return the above error. String object and any attempt to call a method on a null string results in a NullReferenceException. The only reason not to use it is if you want to implement a pattern that would work well for non-nullable value types such as Integer or Decimal, which is exemplified by your answer. Value of an object though.
You are only catching the MySqlException, the exception you are getting is an IndexOutOfRangeException, so execution will stop where the exception is thrown. Public Function CarExists reg As String As Boolean Using constring As New OleDb. This requires less code than using the method, and then performing the operations that you need to generate the single value using the data returned by a. A status of 0 will be returned instead. ToInt32 objValue ; } Thanks Mark and Marc.
Are you 100% sure the table definition you shown us is correct in particular you do have an identity column? You may have to before you can post: click the register link above to proceed. The example is passed a string representing a new value to be inserted into a table, and a string to use to connect to the data source. What's the best way to check for null on an ExecuteScalar? Must use null instead of DbNull. End If Also, most people would say that the use of GoTo is a bad practice and should not be used anymore. .
Finally, your method of determining whether the value exists is just not the way it should be done. This requires less code than using the method, and then performing the operations necessary to generate the single value from the data returned by an. Appreciate all your help and feedback! That means the reference to an Object which is not initialized. A null value is a value that doesnt refer to any object. A status of 0 will be returned instead. This compensation may impact how and where products appear on this site including, for example, the order in which they appear.
To start viewing messages, select the forum that you want to visit from the selection below. Do you really want to use ExecuteScalar? All the three functions i. If you really were going to do it that way and ExecuteScalar might return Nothing then you simply assign the result of ExecuteScalar to a variable and check whether that variable is Nothing. My question is, how do I check for nulls being returned by the above command? When defining a string in a class, dont initialize it to null. Instead, initialize it to the constant String. Thanks Thirdly, you have the line to Close the connection after your Return statement, which means that that line will never be hit. Arne Earl wrote: Hmmm, I can't check DbNull.